1. Field of the Invention
The present invention relates to an optical disk device and a seek method in an optical disk device, and in particular, to an optical disk device which performs a seek operation to move an irradiation position of a light beam on an optical disk to a track in which a target address is present, and a seek method therein.
2. Description of the Related Art
In an optical disk device, a seek operation is performed in which an irradiation position of laser light on an optical disk (light spot position) is moved to a track of a target address (refer to, for example, Japanese Patent Laid-Open Publication No. 2001-256656). In general, in the seek operation, a macro-seek operation in which the irradiation position of the laser light is moved in a wide range along the radial direction of the optical disk is executed. Then, a multiple track jump (N-track jump) is executed in which the irradiation position of laser light is moved along the radial direction of the optical disk by an amount corresponding to a plurality of tracks. Finally, a one-track jump is executed in which the irradiation position of the laser light is moved by one track along the radial direction of the optical disk. In the one-track jump which is performed as the last step, a tracing process is performed every time the irradiation position of the laser light is moved by one track in order to improve the precision of the track jump.
In a seek operation through one-track jump, however, it may become difficult for the light spot to reach the track of the target address for the following reason, for example. When the light spot passes over an area having different reflectivities between adjacent tracks, such as a boundary between a recorded region and an unrecorded region, the balance of the reflection light detected by an optical detector for generating a tracking error signal may be disturbed and off-track of the light spot tends to occur more frequently. When an off-track occurs, the seek operation through one-track jump is again executed toward the track of the target address, but the off-track again occurs when the light spot passes over the area at which the off-track occurred. In this case, it is difficult for the light spot to reach the track of the target address, and, consequently, to quickly and stably perform the seek operation. Such a problem is not limited to a case in which the light spot passes over a boundary between a recorded region and an unrecorded region, and may occur, for example, when the light spot passes over a scratch on a surface of the optical disk.
In the related art of Japanese Patent Laid-Open Publication No. 2001-256656, regarding an optical disk having a boundary region, in which the position information cannot be replayed, between a plurality of data regions, an access over the boundary region is performed through a first jump operation for jumping within the data region and a second jump operation for jumping over the boundary region between the data regions. In this art, however, when the area in which the off-track occurs is not identified, the jump operation for not repeating the off-track is difficult, and moreover, no method for identifying the area in which the off-track occurs is disclosed in this reference.